Thalassospira alkalitolerans sp. nov. and Thalassospira mesophila sp. nov., isolated from a decaying bamboo sunken in the marine environment, and emended description of the genus Thalassospira

<jats:p>Two marine bacteria, designated strains MBE#61<jats:sup>T</jats:sup> and MBE#74<jats:sup>T</jats:sup>, were isolated from a piece of sunken bamboo in the marine environment in Japan. Both of these strains were Gram-stain-negative, but had different cell shapes: MBE#61<jats:sup>T</jats:sup> was spiral, whereas MBE#74<jats:sup>T</jats:sup> was rod-shaped. The temperature, pH and salt concentration ranges for growth of strain MBE#61<jats:sup>T</jats:sup> were 4–38 °C (optimal at 32 °C), pH 4.5–11.0 (optimal at pH 7.0–8.0) and 1–11 % (optimal at 2 %) NaCl, whereas those of strain MBE#74<jats:sup>T</jats:sup> were 4–36 °C (optimal at 30 °C), pH 4.0–10.5 (optimal at pH 7.0–8.0) and 1–12 % (optimal at 4 %) NaCl. Phylogenetic analysis based on partial 16S rRNA gene sequences revealed that both strains belong to the genus <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.852" xlink:type="simple"> <jats:italic>Thalassospira</jats:italic> </jats:ext-link> </jats:named-content> within the class <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="class" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.809" xlink:type="simple"> <jats:italic>Alphaproteobacteria</jats:italic> </jats:ext-link> </jats:named-content>. Similarity between the 16S rRNA gene sequence of strain MBE#61<jats:sup>T</jats:sup> and those of the type strains of species of the genus <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.852" xlink:type="simple"> <jats:italic>Thalassospira</jats:italic> </jats:ext-link> </jats:named-content> was 97.5–99.0 %, and that of strain MBE#74<jats:sup>T</jats:sup> was 96.9–98.6 %; these two isolates were most closely related to <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="species" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.853" xlink:type="simple"> <jats:italic>Thalassospira lucentensis</jats:italic> </jats:ext-link> </jats:named-content> QMT2<jats:sup>T</jats:sup>. However, the DNA–DNA hybridization values between <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="species" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.853" xlink:type="simple"> <jats:italic>T. lucentensis</jats:italic> </jats:ext-link> </jats:named-content> QMT2<jats:sup>T</jats:sup> and strain MBE#61<jats:sup>T</jats:sup> or MBE#74<jats:sup>T</jats:sup> were only 16.0 % and 7.1 %, respectively. The DNA G+C content of strain MBE#61<jats:sup>T</jats:sup> was 54.4 mol%, and that of strain MBE#74<jats:sup>T</jats:sup> was 55.9 mol%. The predominant isoprenoid quinone of the two strains was Q-10 (MBE#61<jats:sup>T</jats:sup>, 97.3 %; MBE#74<jats:sup>T</jats:sup>, 93.5 %). The major cellular fatty acids of strain MBE#61<jats:sup>T</jats:sup> were C<jats:sub>18 : 1</jats:sub>ω7<jats:italic>c</jats:italic> (31.1 %), summed feature 3 comprising C<jats:sub>16 : 0</jats:sub>ω7<jats:italic>c</jats:italic>/iso-C<jats:sub>15 : 0</jats:sub> 2-OH (26.1 %) and C<jats:sub>16 : 0</jats:sub> (20.9 %); those of strain MBE#74<jats:sup>T</jats:sup> were C<jats:sub>16 : 0</jats:sub> (26.2 %), C<jats:sub>17 : 0</jats:sub> cyclo (19.9 %) and C<jats:sub>18 : 1</jats:sub>ω7<jats:italic>c</jats:italic> (12.1 %). On the basis of these results, strain MBE#61<jats:sup>T</jats:sup> and strain MBE#74<jats:sup>T</jats:sup> are considered to represent novel species of the genus <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus" xlink:type="simple"> <jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.852" xlink:type="simple"> <jats:italic>Thalassospira</jats:italic> </jats:ext-link> </jats:named-content>, for which names <jats:italic>Thalassospira alkalitolerans</jats:italic> sp. nov. and <jats:italic>Thalassospira mesophila</jats:italic> sp. nov. are proposed. The type strains are MBE#61<jats:sup>T</jats:sup> ( = JCM 18968<jats:sup>T</jats:sup> = CECT 8273<jats:sup>T</jats:sup>) and MBE#74<jats:sup>T</jats:sup> ( = JCM 18969<jats:sup>T</jats:sup> = CECT 8274<jats:sup>T</jats:sup>), respectively. An emended description of the genus <jats:nam ...